It is known that power diodes or thristors cooled in a chamber which contains a fluorinated hydrocarbon in the liquid state are constituted by a semiconductor wafer sandwiched between two deformable metal membranes which hold and centre the wafer in the ceramic housing which is itself pressed between two metal blocks generally made of copper and which form current inlets for the anode and the cathode.
Omitting the ceramic housing and the deformable membranes, which hinder the dissipation of heat improves the cooling of the wafer, but the blocks and the semiconductor wafer are no longer held mechanically. Therefore, the wafer is no longer mechanically centred with respect to the metal blocks and further, in the case of dismatling, the fragile semiconductor wafer has to be handled.
Supplying the triggers of conventional thyristors is also a problem. Conventional thyristors are disposed at the centre of the wafer and have been controlled, up till now, by leaf springs held inside an axial recess of the cathode block.
The leaf springs had two functions: conveying the trigger control current and pressing the trigger component of the wafer. The disadvantages of such a system are that the end of the spring scrapes the semiconductor material and may damage it subsequent to mechanical vibration, and that the pressure exerted by a leaf spring is not precise.
Preferred embodiments of the present invention mitigate these various drawbacks and generally have the following advantages: firstly, mechanical resistance is provided for the wafer between the copper blocks of the anode and of the cathode, with adequate centring of the wafer, easy handling ans storage and rapid installation in an immersed assembly; and secondly, in the case of thyristors, it improves the precision of the mechanical pressure exerted on the trigger and avoids rapid wear of the latter.